To evaluate the potential role of oxidative stress in the evolution of cervical cancer, including its pre-malignant states.Erythrocytes thiobarbituric acid reactive substances (TBARS) levels, plasma vitamin C and thiol content and total blood δ-ALA-D levels were estimated in 46 untreated cervical cancer and pre-malignant patients and in 46 age–sex-matched controls.Erythrocytes from patients, regardless of disease state, pre-malignant (low squamous intraepithelial lesion—LSIL and high squamous intraepithelial lesion—HSIL) or cancer, showed a significant 2–3 times increase in TBARS levels (P < 0.01). Plasma vitamin C was lower in the carcinoma group (P < 0.01). The reactivation index of δ-aminolevulinate dehydratase (δ-ALA-D) was higher in the patient group, when compared to control (P < 0.01).LSIL, HSIL or cervical cancer can be associated with changes in 3 indicators of oxidative stress: increase in erythrocyte TBARS, ALA-D reactivation index and a decrease in vitamin C content, that may play an important role in carcinogenesis.